While some research supports some positive effects of negative ion exposure, there is no evidence-based medication that supports negative ion therapy. So don't bother getting any household negative ionizers. They can produce hazardous indoor ozone and only waste space and electricity. VOCs are considered indoor pollutants and can cause health problems.
Unfortunately, ionizers are ineffective in reducing VOCs in the air. Air ionizers are designed to help provide cleaner air and they do so through the use of ionized particles. Chamber and field tests found that an ionizing device led to a decrease in some volatile organic compounds (VOC), including xylenes, but an increase in others, more prominently oxygenated VOCs (for example, these ionizers turn on for 8 hours every day, and I have a Therapure TPP300D with UV+ ionizer that is turned on for 8 hours in my living room. As more information is disseminated and presented to the public about the dangers of air ionizers, the more informed consumers will be before purchasing an air purifier, and they are likely to be aware of and avoid these potentially hazardous ionizing air systems.
Since the conflicting data associated with the ionizer remains persistent, I usually keep my ionizer option turned off. However, to get rid of the dangers of second and third hand smoking from my roommate, I now plan to keep my ionizer turned on only for 30-40 minutes when no one is in the room, and then turn off the ionizer before anyone comes in. Ionizer air purifiers are generally safe because ionizers aren't energized enough to be harmful to you. Laboratory tests were conducted with particulate air and gas samples in a large semi-furnished chamber and in a field test with an ionizing device installed in an air handling unit serving an occupied office building.